Thermodynamic limits on drug loading in nanoparticle cores

Area of Science:

• Materials Science
• Chemical Engineering
• Biotechnology

Background:

• Biodegradable block copolymer nanoparticles are promising drug delivery vehicles.
• Current drug loading efficiencies (3-25 wt%) are often low and variable.
• The underlying reasons for low drug loading remain incompletely understood.

Purpose of the Study:

• To develop and validate a quantitative thermodynamic model for drug loading in block copolymer nanoparticles.
• To elucidate the factors limiting drug loading efficiency.
• To provide a predictive tool for optimizing nanoparticle drug loading.

Main Methods:

• Development of a thermodynamic model based on molar free energy of the drug.
• Inclusion of entropic (block copolymer size) and enthalpic (drug-copolymer interaction) terms.
• Incorporation of pressure-volume work, accounting for interfacial tension, as a novel factor.

Main Results:

• The model quantitatively explains observed drug loading values and variability.
• Calculations closely matched experimental data for paclitaxel and other organic solutes.
• The pressure-volume work term was identified as a significant, previously unconsidered factor.

Conclusions:

• The developed thermodynamic model accurately predicts drug loading in block copolymer nanoparticles.
• Understanding these thermodynamic factors is crucial for maximizing drug loading efficiency.
• This model can guide the design of advanced drug delivery systems.